Turning Left While Using Hands-free Cellphone A Dangerous Mix

Making a left-hand turn at a busy intersection while talking on a hands-free cellphone could be the “most dangerous” thing we do on the road due to the high level of brain activation involved, according to a new Canadian study.

Researchers tested healthy young drivers operating a novel driving simulator equipped with a steering wheel, brake pedal and accelerator inside a high-powered functional MRI. This methodology went beyond all previous studies on distracted driving, which used just a joy-stick or trackball or involved patients passively watching scenarios on a screen.

The specialized driving simulator used in the current study allowed researchers to map in real time which parts of the brain were activated or deactivated as the simulator took participants through increasingly difficult driving maneuvers.

The researchers were able to show for the first time that making a left-hand turn requires significant amounts of brain activation, and involves far more areas of the brain than those used in driving on a straight road or other maneuvers.

When the drivers were also involved in a conversation, the part of the brain that controls vision dramatically reduced its activity as the area that controls attention and the monitoring of a conversation was activated.

“Visually, a left-hand turn is quite demanding,” said lead researcher Dr. Tom Schweizer, a neuroscientist and director of the Neuroscience Research Program at St. Michael´s Hospital in Toronto.

“You have to look at oncoming traffic, pedestrians and lights, and coordinate all that. Add talking on a cell phone, and your visual area shuts down significantly, which obviously is key to performing the maneuver,” he said.

The simulation had the drivers make six left turns with oncoming traffic, requiring them to decide when to safely make the turn. It then distracted participants by making them answer a series of true-false audio questions, such as “Does a triangle have four sides?”

The images from the MRIs showed that blood moved from the visual cortex, which controls sight, to the prefrontal cortex, which controls decision-making.

“Brain activity shifted dramatically from the posterior, visual and spatial areas [of the brain] to the prefrontal cortex,” said Dr. Schweizer.